The present invention relates to a leakage prevention device for a valve and, more particularly, to a leakage prevention device for preventing leakage at a portion of a valve receiving a valve rod.
A valve is generally used in pipes to control opening or closing of a fluid passage in the pipes conveying a fluid. When the components of the valve malfunction due to corrosion by the fluid in the pipes or due to aging, maintenance of the valve is required to avoid loss resulting from leakage of the fluid.
FIG. 1 shows a conventional valve 1 including a body 11 having an inlet 111 and an outlet 112 for connection with pipes conveying a fluid. A cover 12 is mounted to a top portion of the body 11 and has an axial hole 121. A valve rod 13 has a lower end extending through the axial hole 121 and connected to a plug 14. A hand wheel 15 is mounted to an upper end of the valve rod 13. When the hand wheel 15 is rotated, the valve rod 13 and the plug 14 move upward or downward to open or close the fluid passage between the inlet 111 and the outlet 112. A plurality of gaskets 16 is stacked in the axial hole 121 and between the valve rod 13 and the cover 12 and is sandwiched between upper and lower bushings 17. A pressing block 18 is mounted on top of the upper bushing 17 to press against the gaskets 16 via the upper bushing 17. The gaskets 16 seal the gap between the valve rod 13 and the inner periphery of the axial hole 121 of the cover 12, avoiding leakage of the fluid via the axial hole 121. The valve 1 further includes a leakage prevention device 10 including a housing 101 and a stretchable tube 102 in the housing 101. A lower end of the housing 101 is fixed to an upper end of the body 11. The lower end of the valve rod 13 extends through the stretchable tube 102. An upper end of the stretchable tube 102 is received in the housing 101. A lower end of the stretchable tube 102 is fixed to the valve rod 13 to move therewith. The stretchable tube 102 can be stretched in the longitudinal direction of the valve 1 and can restore its original shape after the stretching force vanishes. The stretchable tube 102 also isolates the valve rod 13 from the housing 101, further preventing leakage of the fluid via the axial hole 121.
However, the stretchable tube 102 is apt to break at the lower end and the middle portion thereof having large deformation. In an attempt to fix this problem, two stretchable tubes 102 are connected in series. However, large deformation still occurs at the lower end of the set of the stretchable tubes 102, leading to stress concentration and the risk of breakage.